Fluid conducting passage



Dec. 26, 1933. w. s. DIEHL FLUID CONDUCTING PASSAGE Filed Oct. 18

INVENTOR WALTER 5. D/EHL ?NM j ATTO NEY Patented Dec. 26, 1933 UNITED STATES FLUID CONDUCTING PASSAGE Walter S. Diehl,

Washington, D. 0.

Application October 18, 1930. Serial No. 489,685

'1 Claims.

(Granted under the act of March 3, 1883, as

amended April 30,

This invention is applicable to all fluid conduits, and is especially useful to wind tunnels in that it provides a novel method of regulating and controlling the velocity of the air stream, together with novel means for accomplishing such regulation and control.

A principal object of the invention, stated more particularly, is to provide a method and means for reducing the turbulence and eddying eifects caused by the variation in pressure and velocity produced as a fluid stream passes through a tunnel or tube having a non-uniform cross-sectional area as, for example, a Venturi tube.

A further object is to provide a method and means for distributing the fluid flow uniformly throughout the cross-sectional area of the tunnel or tube, thereby preventing formation of a fluid jet along one side of the tube as the fluid passes into the expanding portion of the tube.

The invention further consists in the application to the expanding portion of the tube of a plurality of members adapted to divide the tube into a plurality of sub-tubes, or passages, all of substantially equal volume and equal cross-sectional area at each point along the surface thereof.

As illustrative of the various means by which my invention may be practiced I have shown in the accompanying drawings two methods of applying the inventive concept to tubes of the Venturi type, it being understood that these two illustrations are merely suggestive of numerous other constructions in which the invention may be incorporated. There being no practical benefit to be derived from prolonging'this specification by the insertion of further explanation of such other constructions, they are accordingly omitted.

With the above and other objects in view, the invention consists in the construction, combination and arrangement of parts as will be described more fully hereinafter.

Reference is to be had to the accompanying drawing forming a part of the specification, in which like reference characters indicate corresponding parts throughout the several views, and in which:

Fig. 1 is a longitudinal sectional view through a Venturi tube constructed in accordance with the principles of my invention;

Fig. 2 is a transverse sectional view along the line 2-2 of Fi 1;

Fig. 3 is a transverse sectional view of a tube similar to that shown in Figs. 1 and 2, except that it is square in cross-section rather than circular;

Fig. 4 is a longitudinal sectional view through a Venturi tube, showing a modified construction.

Fig. 5 is an end view of Fig. 4.

Fig. 6 is a plan view of a rectangular Venturi tube equipped with a structure similar to that shown in Figs. 4 and 5. g

Fig. '7 is an end view of the tube shown in Fig. 6.

Reference character 1 designates a Venturi tube of the character commonly employed in wind tunnels for studying the reaction of an air stream upon the surfaces of airplanes and other objects. Venturi tubes are also used extensively for measuring the rate of flow of gases and liquids in pipes, and also for converting the kinetic energy of a moving fluid to potential energy. The present invention is applicable for all such purposes-in short, wherever it is desired to vary the pressure or velocity characteristics of a flowing fluid so that its kinetic energy is converted into potential energy in a short space with a minimum loss of energy.

It is common knowledge among those skilled in such matters that the diverging formation of the walls of a Venturi tube, or of any inclosed passage, produces a turbulent effect upon the air or other fluid as it emerges from the contracted portion of the passage, and for expanding passages of large cone angles the resultant eddy currents disrupt the uniformity of the flow to such an extent as to concentrate the flow into a jet which clings to one side of the expanding passage, leaving the greater portion of the tube unutilizecl. To avoid this action (which would destroy, or at least greatly impair the usefulness of a device of that character) it has been necessary heretofore to keep the angle of divergence of the walls of the passage within seven degrees-that is, a cone angle of fourteen degrees-this angle having been determined as the maximum for which the flow completely fills the expanding passage. The use of this relatively small angle of divergence, however, means that the tube must be relatively long to accomplish the complete Venturi action, with the result that the device as a whole takes up much more space than would be necessaryif shorter tubes could be used. The problem of space is often a. serious one, particularly in wind tunnel operations.

The foregoing difficulties may be surmounted by the use of the present invention which makes it possible to use a muchshorter tunnel or ex panding passage and at the same time obtain the desired Venturi action without any unbalancing of air currents and without sacrificing uniformity of flow. To apply the invention to a Venturi tube such as that shown at 1, I propose to provide a plurality of sub-tubes 2 and 3 of graduated sizes but similar in design to the main tube 1, these sub-tubes being arranged one within the other and held in proper space relationship within the main tube 1, by suitable means as, for example, the bolts or stay members 4 and spacing sleeves 5 (Fig. 2). The latter may be streamlined in contour, if desired, for the purpose of minimizing the resistance to the smooth passage of the fluid.

As shown in Fig. 1 the sub-tubes 2 and 3 serve to divide the air stream (indicated by the arrows) into substantially equal sub-streams, ,or streamlets,.thereby spreading the flow uniformly and preventing the entire body of air from pursuing its natural tendency, which is (under such conditions) to converge into a single jet passing along near the outer wall of the tube.

It will be observed from a study of Figures 1 and 2 that the sub-tubes are so shaped as to preserve a condition of uniform velocity gradient in all sub-tubes at every point along their length. This is the preferred construction, and is accomplished by making the elements along the surface of each sub-tube conform to a curve plotted by taking points on concentric circles at a plurality of sections (one of which is shown in Fig. 2) along the length of the Venturi tube 1, the concentric circles having radii of such length as to divide the corresponding section into subsections all of equal area. Thus circles shown at 2 and 3 divide the section 2-2, constituting Fig. 2, into three equal areas A, B, and C. This relation in Fig. 2 is obtained when the radius of circle 2 is 81.5% of the radius of circle 1 and the radius of circle 3 is 57.6% of the radius of circle 1. In general when there are n passages formed from concentric circles the radii will be given by:

' It is of course to be understood that the number of sub-tubes, or passages, employed may be varied as desired; likewise the shape of the passages may vary. Fig. 3 shows one method of retaining the sub-tubes in place when they are square in cross-section rather than circular. Figures 4 to '7 show the sub-tubes formed by the use of radially disposed and intersecting dividing walls 10 and 11, 12 and 13; the former being mounted in a circular tube and the latter in a rectangular tube. In each case the principle of volumetrically equal sub-passages is preferably adhered to.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of my invention together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combination and relations described, they may be altered in number, construction, and function without interfering with or sacrificing the more general results outlined, and without departing from the scope'of the invention disclosed herein and defined in the appended claims.

The herein described invention may be manu-' in the expanded portion whereby the passages so formed start at approximately the same section near the throat of the venturi and will have equal sectional areas at any cross section along their length.

2. In a wind tunnel venturi, an expanded portion for reducing the velocity of fluid flow, tubes of varying diameters, and means properly spacing said tubes coaxially in the expanded por tion with the starting point of said tubes in approximately the same section near the throat of the venturi whereby passages having equal sectional areas at any cross section along their lengths are formed.

3. A fluid conducting passage having an expanded portion for reducing the velocity of the fluid flow and means in said expanded portion for preventing fluid losses, said means consisting of a plurality of sub-passages having equal sectional areas at any cross section along their length, saidsub-passages having their starting points at approximately the same section and near the beginning of said expanded portion and means for coaxially holding said sub-passage in the proper space relation with each other and 100 11th said expanded portion.

4. In a fluid conductor, an expanded portion having a relatively large angle of divergence for reducing the velocity of fluid flow, tubes of V3.1 ying diameters having an angle of divergence co.- responding to said expanded portion and means properly-spacing said tubes coaxially in the expanded portion with the inner openings of said tubes at approximately the same section and near the point where the conductor starts to expand whereby passages having equal sectional areas at any cross section along their lengths are formed to prevent fluid losses and maintain substantially a uniform distribution of flow.

5. A Venturi tube having a relatively large 115 angle of divergence in the portion for reducing the velocity of fluid flow, means forming subpassages having equal sectional areas at any cross section along their length and means mounting said first mentioned means coaxially in 120 the velocity reducing portion to prevent fluid losses, said subpassages having their inner openings at approximately the same section and near the throat of the venturi.

6. A Venturi tube having a relatively large 125 angle of divergence in the portion for reducing the velocity of fluid flow, tubes of graduate size and means mounting said tubes coaxially in the velocity reducing portion whereby passages having equal sectional areas at any cross section along their lengths are formed to prevent .fluid losses said passages having their inner openings at approximately the same section and near the throat of the venturi.

'7. A Venturi tube having a relatively large angle of divergence in the portion for reducing the velocity of fluid flow, tubes of graduate size and means mounting said tubes coaxially in the velocity reducing portion whereby passages having equal sectional areas at any cross section along their lengths are formed to prevent fluid losses, said mounting means comprising a plurality of radially disposed stay-members passing through the wall of each tube and means for maintaining the walls of the respective tubes in 1 5 fixed spaced relation to each other.

WALTER S. DIEHL. 

